CVE-2021-4128

MEDIUM

6.5

CVSS Score

Published: December 22, 2022 at 12:00 AM UTC

Updated: June 17, 2026 at 04:19 AM UTC

1 product affected across 1 vendorFirefox· also runs on 1 platform

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Severity

MEDIUM6.5

Exploit prediction

EPSS 0.6%

SSVC

PoC

Description

When transitioning in and out of fullscreen mode, a graphics object was not correctly protected; resulting in memory corruption and a potentially exploitable crash.<br>*This bug only affects Firefox on MacOS. Other operating systems are unaffected.*. This vulnerability affects Firefox < 95.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Firefox · Mozilla

95%

v < 95

Affected range stops below 95, so it looks safe — our inference, not a vendor statement

Affected range stops below 95.0, so it looks safe — our inference, not a vendor statement

apple-macos (environment)

Runs on — not affected

The affected product only carries this flaw when running on these platforms. The platforms themselves are not vulnerable.

macOS · Apple

95%

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (2)

ExploitIssue TrackingPatchVendor Advisory

Source: [email protected]

https://bugzilla.mozilla.org/show_bug.cgi?id=1735852

Vendor Advisory

Source: [email protected]

https://www.mozilla.org/security/advisories/mfsa2021-52/

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.5MEDIUMCISA-ADP

Attack Vector: NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: REQUIRED
Scope: UNCHANGED
Confidentiality: NONE
Integrity: NONE
Availability: HIGH

Vector?

Quick Info

StatusMODIFIED

CWE

CWE-416

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